A Global Positioning System (GPS) is a space-based global navigation satellite system that utilizes a network of geo-synchronous satellites that can be utilized by a GPS receiver to determine its location. Many telematics systems incorporate a Global Positioning System (GPS) receiver that can be used to obtain the location of a vehicle at a certain measured time. Using the signals received by the GPS receiver, the heading information of the vehicle can be determined. A GPS receiver can determine velocity information in a variety of ways including, but not limited to, measuring the Doppler shift of the received signals and by comparing the location of a vehicle at a plurality of measured times. The acceleration of the vehicle can be determined as the change in speed divided by the time between the measurements. A GPS receiver's ability to determine acceleration can be limited due to the dependence of the measurement upon factors such as, but not limited to, reception and satellite availability. In addition to location information, a GPS receiver can also be configured to provide time data. However, measurements determined via a GPS receiver can contain errors that affect the accuracy of the measured information. In particular, GPS signals are vulnerable to signal delays, inconsistencies of atmospheric conditions that affect the speed of the GPS signals as they pass through the Earth's atmosphere, and multipath distortions. Additionally, other factors not listed above can influence GPS signals and result in measurement errors.
Telematics is the integrated use of telecommunications and informatics. Telematics units are installed in vehicles to provide a variety of telematics functionality in the vehicle. This functionality includes, but is not limited to, emergency warning systems, navigation functionality, safety warnings, and automated driving assistance. Telematics units are also capable of recording data related to the operation of the vehicle and providing that information for analysis, whether in real-time or during a time when the vehicle is being serviced. This information can be used in a variety of applications, such as fleet tracking, shipment tracking, insurance calculations, and in vehicle management and service.
A common problem encountered during installation of devices in a motor vehicle that connect to the vehicle's electrical system is that the installer may inadvertently connect an ignition input interface to a wire that is not the vehicle ignition line. U.S. Pat. No. 6,163,690, the disclosure of which is incorporated by reference herein in its entirety, notes the potential for the ignition sense line of a hands-free adapter for a mobile phone to be incorrectly connected to a line other than the ignition line due to installer error, which can result in the hands-free adaptor believing the ignition is always on and undesirably draining the vehicle's battery. U.S. Pat. No. 6,163,690 proposes a system that checks the correctness of the ignition sense line installation by monitoring the ignition sense line to determine whether the ignition line is switched off within a predetermined time period. In the event that the hands-free adaptor detects that the ignition line is always on, the hands-free adaptor provides an indication that it has been installed incorrectly.